Picroliv, the iridoid glycoside fraction of Picrorhiza kurroa, selectively augments human T cell response to mycobacterial protein antigens.

Mycobacterial and other intracellular parasitic diseases are characterised by a deficiency in antigen specific host T cell responses. We have studied the effect of Picroliv, a standardised fraction of root and rhizome of Picrorhiza kurroa, on proliferative T cell response to the mycobacterial 'Purified Protein Derivative (PPD)' antigen in subjects infected with or exposed to mycobacteria (tuberculoid leprosy patients and endemic normals). Coculture of their peripheral blood mononuclear cells with the optimal concentration of Picroliv (0.5 microgram/ml) significantly enhanced the proliferative response to 1/10 optimal PPD dose, as determined by [3H] thymidine incorporation, in the group of 'low' responders. The response to PPD of cells from 'high responders' and to PHA (phytohaëmagglutinin, a non-specific T cell mitogen) remained unaffected by Picroliv which did also not induce cell proliferation on its own. The selective, antigen specific augmentation of human T cell response suggests that Picroliv could be useful as an adjunct to chemotherapy or as a short term prophylactic agent.